Multidimensional Esthetic Implant Positioning
implant placement are few. They are often difficult to fabricate and they are not cost effective. Most of the recent computer-generated templates have a metallic stop to control the apical extent of the drill. The optimal axial positioning of the implant head allows the final restoration to emerge naturally through the marginal gingival tissues with no violation to the gingival sulcus (Wheeler 1974), allowing the contours of the restoration to develop in a progressive manner within the periimplant soft tissue housing. As a result, the final prosthetic result appears as if it emerges naturally. Several factors control the location of the implant head in an axial dimension, including (1) the amount of space available for restoration, (2) the topography of the remaining bone, (3) the marginal gingival location of the adjacent natural teeth, and (4) the selected implant diameter. The optimal axial location of the implant head is necessary due to the anatomical difference between the fixture morphology and that of the natural tooth at the cervical level. A morphological transition from the narrow circular implant neck from the implant head to that of the natural tooth form is naturally required. The reference location of all axial implant positioning is an imaginary line connecting the gingival zeniths of the adjacent natural teeth. There is a greater urgency for restoring natural gingival contours surrounding the new restorations when a natural tooth reference is missing and multiple adjacent implants are to be used. These implants should be placed at the alveolar crest within the circumference of the missing teeth to be restored. This enables the clinician to develop appropriate natural embrasures on both sides adjoining the restorations and duplicate a natural gingival profile (Potashnick 1998). The ideal apicoincisal implant positioning places the implant head 2 mm to 3 mm apical to the line connecting the gingival zeniths of the adjacent natural teeth. This subsequently allows “running room” throughout the biological width of the implant when it is correctly positioned in an apicoincisal plane (Parel and Sullivan 1989), as shown in Figure 4.21. The “running room” is a space of 2 mm to 3 mm in depth and it surrounds the implant head circumferentially, as shown in Figure 4.22. This room allows for stacking or building up of prosthetic components to create the natural gingival emergence of the final restoration. If any modification or expansion of the gingival tissues to match the original crown size takes place in this particular space, the progressive use of the provisional restoration will develop the original cross-sectional shape of the missing natural tooth. The use of anatomical abutments has not proven to be more effective than the progressive use of the provisional restoration. Because the gingival tissue does not have a memory to keep its original dimensions without existing support, the peri-implant soft tissue tends to collapse and regain its original circular shape (due to the
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pressure from the circular collagen fibers surrounding the biological seal) upon its removal from the gingival sulcus. Clinically speaking, natural biological contours could be replicated without the need for anatomical abutments. Provisional prostheses have proven to give an optimal gingival influence with great clinical predictability. (See Figure 4.23.) Implant diameter has an inverse relationship to the amount of subgingival sinking. It influences the amount
Figure 4.21. An illustration showing the ideal axial positioning of the implant, 2–3 mm from the line connecting the gingival zenith of the natural teeth.
Figure 4.22. The ideal distance from the gingival zenith to the implant head. The blue line represents the gingival zenith, and the green line represents the optimal implant axial position.